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stream: move WHATWG byte-stream helpers to C++ #63570

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e2c7b65
stream: move WHATWG byte-stream helpers to C++
mcollina May 31, 2026
606d472
stream: move byte-stream helpers to util binding
mcollina Jun 15, 2026
39f0fbd
fixup
mcollina Jun 15, 2026
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40 changes: 22 additions & 18 deletions lib/internal/webstreams/readablestream.js
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Original file line number Diff line number Diff line change
Expand Up @@ -93,9 +93,6 @@ const {
} = require('internal/streams/utils');

const {
ArrayBufferViewGetBuffer,
ArrayBufferViewGetByteLength,
ArrayBufferViewGetByteOffset,
AsyncIterator,
canCopyArrayBuffer,
cloneAsUint8Array,
Expand All @@ -106,6 +103,7 @@ const {
enqueueValueWithSize,
extractHighWaterMark,
extractSizeAlgorithm,
getArrayBufferView,
getNonWritablePropertyDescriptor,
isBrandCheck,
kState,
Expand Down Expand Up @@ -688,8 +686,9 @@ class ReadableStreamBYOBRequest {
'This BYOB request has been invalidated');
}

const viewByteLength = ArrayBufferViewGetByteLength(view);
const viewBuffer = ArrayBufferViewGetBuffer(view);
const arrayBufferView = getArrayBufferView(view);
const viewBuffer = arrayBufferView[0];
const viewByteLength = arrayBufferView[2];
const viewBufferByteLength = ArrayBufferPrototypeGetByteLength(viewBuffer);

if (ArrayBufferPrototypeGetDetached(viewBuffer)) {
Expand Down Expand Up @@ -980,8 +979,9 @@ class ReadableStreamBYOBReader {
}
validateObject(options, 'options', kValidateObjectAllowObjectsAndNull);

const viewByteLength = ArrayBufferViewGetByteLength(view);
const viewBuffer = ArrayBufferViewGetBuffer(view);
const arrayBufferView = getArrayBufferView(view);
const viewBuffer = arrayBufferView[0];
const viewByteLength = arrayBufferView[2];

if (isSharedArrayBuffer(viewBuffer)) {
throw new ERR_INVALID_ARG_VALUE(
Expand Down Expand Up @@ -1198,8 +1198,9 @@ class ReadableByteStreamController {
if (!isReadableByteStreamController(this))
throw new ERR_INVALID_THIS('ReadableByteStreamController');
validateBuffer(chunk);
const chunkByteLength = ArrayBufferViewGetByteLength(chunk);
const chunkBuffer = ArrayBufferViewGetBuffer(chunk);
const arrayBufferView = getArrayBufferView(chunk);
const chunkBuffer = arrayBufferView[0];
const chunkByteLength = arrayBufferView[2];

if (isSharedArrayBuffer(chunkBuffer)) {
throw new ERR_INVALID_ARG_VALUE(
Expand Down Expand Up @@ -2745,9 +2746,10 @@ function readableByteStreamControllerPullInto(
assert(minimumFill >= elementSize && minimumFill <= view.byteLength);
assert(minimumFill % elementSize === 0);

const buffer = ArrayBufferViewGetBuffer(view);
const byteOffset = ArrayBufferViewGetByteOffset(view);
const byteLength = ArrayBufferViewGetByteLength(view);
const arrayBufferView = getArrayBufferView(view);
const buffer = arrayBufferView[0];
const byteOffset = arrayBufferView[1];
const byteLength = arrayBufferView[2];
const bufferByteLength = ArrayBufferPrototypeGetByteLength(buffer);

let transferredBuffer;
Expand Down Expand Up @@ -2888,9 +2890,10 @@ function readableByteStreamControllerEnqueue(controller, chunk) {
stream,
} = controller[kState];

const buffer = ArrayBufferViewGetBuffer(chunk);
const byteOffset = ArrayBufferViewGetByteOffset(chunk);
const byteLength = ArrayBufferViewGetByteLength(chunk);
const arrayBufferView = getArrayBufferView(chunk);
const buffer = arrayBufferView[0];
const byteOffset = arrayBufferView[1];
const byteLength = arrayBufferView[2];

if (closeRequested || stream[kState].state !== 'readable')
return;
Expand Down Expand Up @@ -3183,9 +3186,10 @@ function readableByteStreamControllerRespondWithNewView(controller, view) {
const desc = pendingPullIntos[0];
assert(stream[kState].state !== 'errored');

const viewByteLength = ArrayBufferViewGetByteLength(view);
const viewByteOffset = ArrayBufferViewGetByteOffset(view);
const viewBuffer = ArrayBufferViewGetBuffer(view);
const arrayBufferView = getArrayBufferView(view);
const viewBuffer = arrayBufferView[0];
const viewByteOffset = arrayBufferView[1];
const viewByteLength = arrayBufferView[2];
const viewBufferByteLength = ArrayBufferPrototypeGetByteLength(viewBuffer);

if (stream[kState].state === 'closed') {
Expand Down
57 changes: 13 additions & 44 deletions lib/internal/webstreams/util.js
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Original file line number Diff line number Diff line change
@@ -1,19 +1,14 @@
'use strict';

const {
ArrayBufferPrototypeGetByteLength,
ArrayBufferPrototypeGetDetached,
ArrayBufferPrototypeSlice,
ArrayPrototypePush,
ArrayPrototypeShift,
AsyncIteratorPrototype,
MathMax,
NumberIsNaN,
PromisePrototypeThen,
ReflectApply,
ReflectGet,
Symbol,
Uint8Array,
} = primordials;

const {
Expand All @@ -27,16 +22,19 @@ const {
} = internalBinding('buffer');

const {
inspect,
} = require('util');

const {
canCopyArrayBuffer,
cloneAsUint8Array,
constants: {
kPending,
},
getArrayBufferView,
getPromiseDetails,
} = internalBinding('util');

const {
inspect,
} = require('util');

const assert = require('internal/assert');

const {
Expand Down Expand Up @@ -87,38 +85,11 @@ function customInspect(depth, options, name, data) {
return `${name} ${inspect(data, opts)}`;
}

// These are defensive to work around the possibility that
// the buffer, byteLength, and byteOffset properties on
// ArrayBuffer and ArrayBufferView's may have been tampered with.

function ArrayBufferViewGetBuffer(view) {
return ReflectGet(view.constructor.prototype, 'buffer', view);
}

function ArrayBufferViewGetByteLength(view) {
return ReflectGet(view.constructor.prototype, 'byteLength', view);
}

function ArrayBufferViewGetByteOffset(view) {
return ReflectGet(view.constructor.prototype, 'byteOffset', view);
}

function cloneAsUint8Array(view) {
const buffer = ArrayBufferViewGetBuffer(view);
const byteOffset = ArrayBufferViewGetByteOffset(view);
const byteLength = ArrayBufferViewGetByteLength(view);
return new Uint8Array(
ArrayBufferPrototypeSlice(buffer, byteOffset, byteOffset + byteLength),
);
}

function canCopyArrayBuffer(toBuffer, toIndex, fromBuffer, fromIndex, count) {
return toBuffer !== fromBuffer &&
!ArrayBufferPrototypeGetDetached(toBuffer) &&
!ArrayBufferPrototypeGetDetached(fromBuffer) &&
toIndex + count <= ArrayBufferPrototypeGetByteLength(toBuffer) &&
fromIndex + count <= ArrayBufferPrototypeGetByteLength(fromBuffer);
}
// getArrayBufferView, canCopyArrayBuffer, and cloneAsUint8Array are
// implemented in src/node_util.cc via direct V8 API calls. They are immune to
// user tampering of typed-array prototypes (matching the defensive behavior of
// the previous Reflect.get-based JS implementation) and faster on hot
// byte-stream paths.

function isBrandCheck(brand) {
return (value) => {
Expand Down Expand Up @@ -206,9 +177,6 @@ function lazyTransfer() {
}

module.exports = {
ArrayBufferViewGetBuffer,
ArrayBufferViewGetByteLength,
ArrayBufferViewGetByteOffset,
AsyncIterator,
canCopyArrayBuffer,
cloneAsUint8Array,
Expand All @@ -219,6 +187,7 @@ module.exports = {
enqueueValueWithSize,
extractHighWaterMark,
extractSizeAlgorithm,
getArrayBufferView,
getNonWritablePropertyDescriptor,
isBrandCheck,
isPromisePending,
Expand Down
45 changes: 33 additions & 12 deletions src/node_buffer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1480,11 +1480,12 @@ void CopyArrayBuffer(const FunctionCallbackInfo<Value>& args) {
// args[3] == Source ArrayBuffer Offset
// args[4] == bytesToCopy

Environment* env = Environment::GetCurrent(args);
CHECK(args[0]->IsArrayBuffer() || args[0]->IsSharedArrayBuffer());
CHECK(args[1]->IsUint32());
CHECK(args[1]->IsNumber());
CHECK(args[2]->IsArrayBuffer() || args[2]->IsSharedArrayBuffer());
CHECK(args[3]->IsUint32());
CHECK(args[4]->IsUint32());
CHECK(args[3]->IsNumber());
CHECK(args[4]->IsNumber());

void* destination;
size_t destination_byte_length;
Expand All @@ -1495,16 +1496,36 @@ void CopyArrayBuffer(const FunctionCallbackInfo<Value>& args) {
size_t source_byte_length;
std::tie(source, source_byte_length) = DecomposeBufferToParts(args[2]);

uint32_t destination_offset = args[1].As<Uint32>()->Value();
uint32_t source_offset = args[3].As<Uint32>()->Value();
size_t bytes_to_copy = args[4].As<Uint32>()->Value();

CHECK_GE(destination_byte_length - destination_offset, bytes_to_copy);
CHECK_GE(source_byte_length - source_offset, bytes_to_copy);
int64_t destination_offset;
int64_t source_offset;
int64_t bytes_to_copy;
if (!args[1]->IntegerValue(env->context()).To(&destination_offset) ||
!args[3]->IntegerValue(env->context()).To(&source_offset) ||
!args[4]->IntegerValue(env->context()).To(&bytes_to_copy)) {
return;
}

uint8_t* dest = static_cast<uint8_t*>(destination) + destination_offset;
uint8_t* src = static_cast<uint8_t*>(source) + source_offset;
memcpy(dest, src, bytes_to_copy);
CHECK_GE(destination_offset, 0);
CHECK_GE(source_offset, 0);
CHECK_GE(bytes_to_copy, 0);

const uint64_t destination_offset_u =
static_cast<uint64_t>(destination_offset);
const uint64_t source_offset_u = static_cast<uint64_t>(source_offset);
const uint64_t bytes_to_copy_u = static_cast<uint64_t>(bytes_to_copy);
const uint64_t destination_byte_length_u = destination_byte_length;
const uint64_t source_byte_length_u = source_byte_length;
CHECK_LE(destination_offset_u, destination_byte_length_u);
CHECK_LE(source_offset_u, source_byte_length_u);
CHECK_LE(bytes_to_copy_u, destination_byte_length_u - destination_offset_u);
CHECK_LE(bytes_to_copy_u, source_byte_length_u - source_offset_u);

const size_t destination_offset_s = static_cast<size_t>(destination_offset_u);
const size_t source_offset_s = static_cast<size_t>(source_offset_u);
const size_t bytes_to_copy_s = static_cast<size_t>(bytes_to_copy_u);
uint8_t* dest = static_cast<uint8_t*>(destination) + destination_offset_s;
uint8_t* src = static_cast<uint8_t*>(source) + source_offset_s;
memcpy(dest, src, bytes_to_copy_s);
}

// Converts a number parameter to size_t suitable for ArrayBuffer sizes
Expand Down
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